As an example of such construction machines, a hybrid construction machine described in Japanese Unexamined Patent Publication No. 2012-213281 is known.
The hybrid construction machine includes an engine, a generator motor connected to an output shaft of the engine, and a hydraulic pump connected to the output shaft of the engine via the generator motor.
The generator motor operates as a power generator using power from the engine and also operates as a motor when electric power from an electric power source such as an electric power storage device is supplied thereto to assist the engine.
Specifically, the generator motor includes a stator, a rotor which rotates relative to the stator, and a housing which houses the stator and the rotor.
The housing includes a housing main body (a pump-side housing) which encloses a periphery of the stator and the rotor and a cover (a supporting member) which is attached to an end surface of the housing main body so as to cover an opening formed on an end surface on an opposite side to the engine (a hydraulic pump side) of the housing main body.
As described earlier, the generator motor internally generates electric power and also supplies electric power to and receives electric power from a power storage device or the like. Therefore, when water exists in the housing of the generator motor, a failure such as a short-circuit of an electric circuit provided inside the generator motor and corrosion of components of the generator motor may occur.
In particular, since the rotor and the stator generate heat during activation of the generator motor, a temperature difference may arise between the temperature inside the housing and the temperature outside the housing. When dew condensation occurs inside the housing due to the temperature difference, water created by the dew condensation may cause a failure in the generator motor.